During fuel injector assembly, it is known to locate a valve seat subassembly on a machined shoulder in the nose of the fuel injector valve body. The axial shoulder dimension is used to locate the valve seat subassembly and therefore determines armature position.
During assembly of the valve seat subassembly into the nose of the valve body, the seat subassembly, including a valve seat, swirl disk and lower needle guide, is located or stacked up against the machined shoulder of the valve body. The nose of the valve body is crimped to hold the seat subassembly. An alignment pin on a fixture is used to align the seat subassembly components and valve body. Resistance welding is used to weld the seat subassembly and valve body together.
In this arrangement, the stack up height of the lower needle guide, swirl disk and valve seat, together with the depth of the pocket adjacent the machined shoulder in the nose of the injector valve body is critical. Crimping the valve body nose can cause misalignment of the valve seat components relative to each other and relative to the valve body. Also, the use of resistance welding close to the center holes in the lower needle guide, swirl disk and valve seat distorts the valve seat subassembly.